1. Field of the Invention
The current invention relates to a hydrodynamic machine, in particular a hydrodynamic coupling.
2. Description of the Related Art
Hydrodynamic couplings that are equipped with a revolving bladed primary wheel and a stationary or also revolving bladed secondary wheel—referred to as impeller and turbine wheel in the case of a hydrodynamic coupling, and referred to as rotor and stator or rotor and counter-rotation rotor in the case of a hydrodynamic retarder—conventionally include antifriction bearings for mounting the revolving components. However, hydrodynamic couplings have already been suggested that have plain bearings, lubricated with the working medium. See for example DE 101 20 477 B4 and EP 1 633 991 B1.
DE 101 20 477 B4 moreover suggests to design the combined thrust and radial bearings as plain bearings in a hydrodynamic coupling, whereby the working medium is used as the lubricant and the supply to the bearings occurs from the working medium supply of the clutch.
In the case of hydrodynamic couplings having plain bearings that are lubricated with working medium it cannot be reliably ruled out that the lubricant supply to the bearings is not interrupted or considerably reduced in certain operational conditions. European patent specification EP 1 633 991 B1 specifically points out that a supply to the bearings occurs only when a certain pressure in the system is reached, in order to achieve a more rapid filling of the working chamber of the hydrodynamic coupling with working medium. Moreover it is possible with known couplings that, for example, the drive shaft is rotated in towing operation before the lubricant supply of the bearing is activated, so that there is a risk of damaging the bearings.
Finally, the lubricant supply can intermittently fail, resulting in the bearings running dry.
The aforementioned issue could conventionally only be solved in that relatively expensive plain bearings were used that permitted a temporary dry run. However, this resulted in undesirable high production costs of the hydrodynamic coupling.